Short diary, unfortunately came in late from my evening run and Erin Burnett was playing forensic technician on CNN with some dude playing with a "hologram" of the Boylston street scene. Erin states in her best "I know everything" voice, that runners have chips on them that broadcast their location "every millisecond" and the "police will use that to see where people were when the explosions happened" and the the dude with the hologram waves his hands over the north-side of Boylston saying that "they'll coordinate runners positions with their families here (waving away) to ask them what they saw."
Amateur hour doesn't get much better than this.
For anyone who hasn't participated in a running event, you get a small RFID chip on your bib number. The RFID is read at various locations throughout the race (the arches you see at 10-15 locations) and the time since the start (your split) is recorded, this is how your friends can track you during the race.